It is occasionally desirable to remove air from the interior of a fluid system to the exterior of the fluid system through an air valve. In many cases, it is also desirable that air from the exterior of the fluid system be prevented from entering the fluid system through the same air valve when air is not being removed from the interior of the fluid system through the air valve. When air is being removed from the fluid system, the air valve is open, and when air is not being removed from the fluid system, the air valve is closed.